In the art of respiration devices, there are a well known variety of respiratory masks which cover the nose and/or mouth of a human user in order to provide a continuous seal around the nasal and/or oral areas of the user's face such that gas may be provided at positive pressure within the mask for consumption by the user. The uses for such masks range from high altitude breathing (i.e., aviation applications) to mining and fire fighting applications, to various medical diagnostic and therapeutic applications.
One requisite of such respiratory masks has been that they provide an effective seal against the user's face to prevent leakage of the gas being supplied. Commonly, in prior mask configurations, a good mask-to-face seal has been attained in many instances only with considerable discomfort for the user. This problem is most crucial in those applications, especially medical applications, which require the user to wear such a mask continuously for hours or perhaps even days. In such situations, the user will not tolerate the mask for long durations and optimum therapeutic or diagnostic objectives thus will not be achieved, or will be achieved with great difficulty and considerable user discomfort.
In common with prior art designs, is an inability to attach the plenum, supplying gases to the user, to the head strap such that the position of the plenum may be altered without distorting the position of the mask on the user's face.
U.S. Pat. No. 6,347,631 and U.S. Pat. No. 6,516,802 are examples of prior art that provide a means of rigidly attaching a gas plenum to the hear gear which utilises a cantilever adjustment mechanism. The cantilever adjustment mechanism provides a means of adjusting the headgear and any movement of the gas plenum is achieved by sliding the plenum through a plurality of rings on the cantilever arrangement.